1. Field of the Invention
The present invention relates to a magnetic tape apparatus for the recording and playback of video signals with a rotating one head drum, which is surrounded by the recording tape like an omega over an angle of about 360 degrees.
2. Brief Description of the Background of the Invention Including Prior Art
Video recording can be classified into systems derived from a quadruplex video tape recorder and into those derived from a helical recording system. Helical scanning is obtained by wrapping the magnetic tape around a drum in a spiral fashion and employing a slant track for the recording. The drum is split into two by a slot which passes around its circumference and the recording head or recording heads rotate in the drum. If the wrap angle is chosen with the correct degree of rise from one side of the drum to the other, thru the combination of forward motion of the tape and of the rotation of the head across the tape produces a track which is aligned to the horizontal by a small angle of say for example 3 degrees.
Various conventional recorders record and play back half picture or field one after another with a head. The position of the track is the same. The head has to be surrounded like an omega. It performs for each recording track one rotation. This results in 50 rotations per second with the same number of half pictures. It is necessary to provide a relatively large track distance in order to keep the interfering cross talk to a minimum (grass). The recording density achieved in this way is not satisfactory and the use of tape length is very high. Compare for example the Poehler German Patent Applications Laid Open DE-OS No. 2,730,727; DE-OS No. 2,831,333; and DE-OS NO. 2,924,115.
An improvement of these deficiencies has been attempted according to German Patent Application Laid Open DE-OS No. 2,819,958 by providing the head slot not as a straight line, but at least in the edge regions as curved and angled at oppositely running angles.
Known two-head video recorders comprises a so-called azimuth offset of the head gaps of for example a plus-minus 6 degrees in the VHS system and can dispense nearly completely with track distance spacings without the occurrence of cross-talk in a substantial amount.
It is known from German Pat. No. 2,711,703 to realize a track follow control readjustament with a so-called level correction of the heads based on bending supports for a one head drum with an omega shaped magnetic tape wrapping around the drum. No azimuth offset is provided here. The track follow control adjustment is to permit all kinds of conceivable trick scans.
An azimuth offset of the two heads employed is provided in order to avoid cross-talk according to German Pat. No. 2,838,003. A track follow control (height level correction) with piezo-ceramic PXC-elements was also taught in this reference. Characteristic signals of four fixed frequencies are keyed in during recording in the two video frequency regions and they are employed during sensing and playback for controlling of the heads. The system has become known as DTF (dynamic track following).
All these constructions, systems and apparatus have their quirks and deficiencies. However, they do not provide a solution to a single head video recorder of smallest construction size.